The Windows Update Agent on each individual computer reaches out to the WSUS (or Microsoft) server and asks what updates are available for the products that the Agent finds on the system. WSUS (or Microsoft) will then respond with all updates that are available
and approved that are requested by the Windows Update Agent locally on the system.
If WSUS does not have the product checked in options, it cannot give any information to the client system about it (eg, if you have Office 2013 on the client system but only have Office 2010 checked in the products on WSUS, Office 2013 will never update.)
At the same time, if you have multiple products checked in WSUS where the client system only has 1 or 2 of them, then ONLY those updates that are needed by the client computer will download and install. (eg, if you have both Office 2010 and Office 2013 checked
in WSUS along with Windows 7 and Windows 10, and a Windows 10 client with Office 2013 requests updates, the system will only download Windows 10 updates with Office 2013 updates as those are the only ones that are 'needed' by the client system.)
Adam Marshall, MCSE: Security
https://www.ajtek.ca
Microsoft MVP - Windows and Devices for IT
How to Stop WSUS Unnessessary Updates
